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Sema: disallow slicing many-item pointer with different sentinel

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This change prevents adding or changing the sentinel in the type of a
many-item pointer via the slicing syntax `ptr[a.. :S]`.
This commit is contained in:
dweiller 2024-12-31 16:07:08 +11:00 committed by Matthew Lugg
parent bce6a7c215
commit 19fc5f4fb2
3 changed files with 50 additions and 3 deletions
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32
src/Sema.zig
View File

@ -31876,6 +31876,38 @@ fn analyzeSlice(
break :e try sema.coerce(block, .usize, uncasted_end, end_src);
} else break :e try sema.coerce(block, .usize, uncasted_end_opt, end_src);
}
// when slicing a many-item pointer, if a sentinel `S` is provided as in `ptr[a.. :S]`, it
// must match the sentinel of `@TypeOf(ptr)`.
sentinel_check: {
if (sentinel_opt == .none) break :sentinel_check;
const provided = provided: {
const casted = try sema.coerce(block, elem_ty, sentinel_opt, sentinel_src);
try checkSentinelType(sema, block, sentinel_src, elem_ty);
break :provided try sema.resolveConstDefinedValue(
block,
sentinel_src,
casted,
.{ .simple = .slice_sentinel },
);
};
if (ptr_sentinel) |current| {
if (provided.toIntern() == current.toIntern()) break :sentinel_check;
}
return sema.failWithOwnedErrorMsg(block, msg: {
const msg = try sema.errMsg(sentinel_src, "sentinel-terminated slicing of many-item pointer must match existing sentinel", .{});
errdefer msg.destroy(sema.gpa);
if (ptr_sentinel) |current| {
try sema.errNote(sentinel_src, msg, "expected sentinel '{f}', found '{f}'", .{ current.fmtValue(pt), provided.fmtValue(pt) });
} else {
try sema.errNote(ptr_src, msg, "type '{f}' does not have a sentinel", .{slice_ty.fmt(pt)});
}
try sema.errNote(src, msg, "use @ptrCast to cast pointer sentinel", .{});
break :msg msg;
});
}
return sema.analyzePtrArithmetic(block, src, ptr, start, .ptr_add, ptr_src, start_src);
};

3
test/behavior/slice.zig
View File

@ -628,9 +628,6 @@ test "slice syntax resulting in pointer-to-array" {
comptime assert(@TypeOf(ptr[1..][0..2]) == *[2]u8);
comptime assert(@TypeOf(ptr[1..][0..4]) == *[4]u8);
comptime assert(@TypeOf(ptr[1..][0..2 :4]) == *[2:4]u8);
comptime assert(@TypeOf(ptr[1.. :0][0..2]) == *[2]u8);
comptime assert(@TypeOf(ptr[1.. :0][0..4]) == *[4]u8);
comptime assert(@TypeOf(ptr[1.. :0][0..2 :4]) == *[2:4]u8);
var ptr_z: [*:0]u8 = &array;
comptime assert(@TypeOf(ptr_z[1..][0..2]) == *[2]u8);

18
test/cases/compile_errors/slice_of_many-item_pointer_preserves_sentinel.zig Normal file
View File

@ -0,0 +1,18 @@
comptime {
var ptr: [*]const u8 = undefined;
_ = ptr[0.. :0];
}
comptime {
var ptrz: [*:0]const u8 = undefined;
_ = ptrz[0.. :1];
}
// error
//
// :3:18: error: sentinel-terminated slicing of many-item pointer must match existing sentinel
// :3:9: note: type '[*]const u8' does not have a sentinel
// :3:12: note: use @ptrCast to cast pointer sentinel
// :8:19: error: sentinel-terminated slicing of many-item pointer must match existing sentinel
// :8:19: note: expected sentinel '0', found '1'
// :8:13: note: use @ptrCast to cast pointer sentinel